DOHA (Reuters) – Top oil exporters Russia and Saudi Arabia agreed on Tuesday to freeze output levels but said the deal was contingent on other producers joining in – a major sticking point with Iran absent from the talks and determined to raise production. The Saudi, Russian, Qatari and Venezuelan oil ministers announced the proposal after a previously undisclosed meeting in Doha. It could become the first joint OPEC and non-OPEC deal in 15 years, aimed at tackling a growing oversupply of crude and helping prices recover from their lowest in over a decade.